Tire treads need to be provided with high levels of mainly fuel efficiency, abrasion resistance, wet grip performance and other properties, and various methods for improving these properties have been considered.
For example, fuel efficiency is known to be improved by introducing a functional group having an affinity for filler into the polymer end; abrasion resistance is known to be improved by use of a high molecular weight polymer having a molecular weight of 250,000 or more; and wet grip performance is known to be improved by use of a polymer having a high glass transition temperature (Tg).
However, the introduction of a functional group having an affinity for filler, the use of a high molecular weight polymer, and the use of a polymer having a high Tg resulting from increased styrene content all result in rubber compositions having increased hardness and therefore poor processability.
Patent Literature 1 discloses a tire rubber composition of which the fuel efficiency, the abrasion resistance, and the wet grip performance are improved by adding a liquid resin having a softening point of −20 to 45° C. and a certain silica. However, there is still room for improvement in terms of achieving balanced improvements in these properties while providing good processability.